**Question:** In a person who has fasted for 5 days all are seen except

A. Hyperglycaemia
B. Acidosis
C. Dehydration
D. Hypokalaemia

**Correct Answer:** **Hypokalaemia**

**Core Concept:** Fasting leads to a decrease in insulin secretion and an increase in glucagon secretion, which results in increased glucose production and utilization, decreased protein catabolism, and impaired potassium excretion.

**Why the Correct Answer is Right:** Hypokalaemia occurs during fasting due to several reasons:

1. **Decreased potassium excretion**: Fasting leads to impaired renal potassium excretion, as the increased glucagon levels decrease the reabsorption of potassium in the distal renal tubule.
2. **Increased potassium release**: Hypokalaemia can also result from increased potassium release from skeletal muscles due to decreased glucose uptake by muscles, leading to muscle cell depolarization and potassium release.
3. **Decreased potassium intake**: Since fasting patients avoid food intake, they consume less potassium-rich foods, further contributing to hypokalaemia.

**Why Each Wrong Option is Incorrect:**

1. **Hyperglycaemia**: Fasting causes a temporary increase in blood glucose levels due to the activation of gluconeogenesis and glycogenolysis.
2. **Acidosis**: Fasting does not lead to significant acidosis unless the person is unable to maintain fluid balance or has a concurrent disease process. Fasting-induced acidosis is counteracted by the kidneys excreting bicarbonate ions and retaining acidic substances.
3. **Dehydration**: While dehydration is a potential consequence of fasting, it is not the primary reason for hypokalaemia. Hypokalaemia occurs due to the reasons mentioned above, primarily impaired potassium excretion and increased potassium release.

**Clinical Pearl:** Hypokalaemia should be suspected in patients undergoing prolonged fasting or any other situations with decreased potassium intake and/or increased potassium-losing conditions. Monitoring serum potassium levels can help identify and manage this electrolyte imbalance, preventing complications like neuromuscular weakness, cardiac arrhythmias, and tetany.